Silicon-29 NMR aids study of lignins

Abstract

Silicon nuclear magnetic resonance spectra of silylated lignins offer numerous advantages for studying the complex wood polymers, says chemist John Ralph of the Department of Agriculture's dairy forage research center in Madison, Wis. Compared with carbon-13 NMR, silicon-29 spectra offer greater sensitivity and can be obtained faster, he says. Ralph presented his research at a symposium on NMR characterization of plant cell wall polymers that focused primarily on lignin. Although organic chemists have been studying lignin for decades, its structure is so complex and varies so much from tree to tree that many details remain to be filled in, says Lawrence L. Landucci, a chemist with USDA's forest products laboratory in Madison, who was one of the symposium organizers. The fastpaced development of new NMR techniques in the past decade has prompted lignin chemists to reinvestigate the technique. Lignin contains numerous phenolic, primary, and secondary hydroxyl groups that can form silyl ethers, Ralph points ...